The present invention relates to pile fabrics and more particularly to a pile fabric in which the yarn is a texturized yarn which is a stable plied yarn which is formed by self-twisting from a plurality of false twisted single yarns and joined at the nodes of the single false twisted yarns.
The use of artificial "man-made" fibers, as a replacement for natural fibers such as wool and cotton, is increasingly widespread. The use of artificial fibers is especially widespread in carpet manufacture where their ease of care, durability, lightweight strength and resistance to weather exposure, sunlight, chemicals, moths and other insects, along with color-fastness of such fibers, pose distinct advantages.
However, one drawback with artificial fibers is that they do not, without special processing, possess the bulk associated with wool.
Another difficulty with carpets of artificial fibers may be a tendency to "streak" or form lines which detract from the carpet's appearance. Such streaking may be due to the pile loops or tufts forming into a somewhat parallel alignment, giving a directional effect. Such streaking can be caused by twist variations between tufts, certain constructions accentuating the optical effects of such twist variations. In some cases if the singles and plied yarns of the carpet are uniformly twisted in one direction, the tendency toward parallel alignment and streaking may be more pronounced.
Generally speaking, as methods to add bulk or other desirable properties to yarn, false-twisting and self-twisting and the yarns thereby produced have received considerable attention in recent years and reference is made to the following documents in which these yarns, the techniques for producing them, and specific apparatus related thereto are discussed:
"Self-Twist Yarn", D. E. Henshaw Merrow Publishing Co. Ltd., Watford, Herts, England, 1971 PA1 U.s. pat. No. 2,986,867; Berry PA1 U.s. pat. RE No. 27,717; Breen et al PA1 U.s. pat. No. 3,225,533; Henshaw PA1 U.s. pat. No. 3,306,023; Henshaw et al PA1 U.s. pat. No. 3,353,344; Clendening, Jr. PA1 U.s. pat. No. 3,434,275; Backer et al PA1 U.s. pat. No. 3,507,108; Yoshimura et al PA1 U.s. pat. No. 3,717,988; Walls PA1 U.s. pat. No. 3,775,955; Shah PA1 U.s. pat. No. 3,940,917; Strachan.
While this is by no means an exhaustive listing of patents or literature references on this subject, the foregoing represent references which discuss the principles and techniques which are part of the prior art.
As will be recognized from these and other references relating to this art, there are a number or problems inherent in producing yarn using self-twist techniques, these problems being related in part to the fact that the yarn tends to be relatively unstable due to the opposite twists in singles being able to cancel each other through the node area. In this regard, the above-cited U.S. Pat. No. 3,434,275 to Backer et al suggests joining regions of twist reversal. Also, in the production of self-twist yarn, the yarn tension and other parameters involved in the production are highly critical and must be closely controlled.
In Berry U.S. Pat. No. 2,986,867 a singles yarn has a unidirectional twist which may be either an "S" or "Z" twist. The twist may vary in degree and may be reversed in some portions when the singles yarn is plied into a composite plied yarn. The plying twist is derived in two steps: first a varying unidirectional ply twist is put into the yarn and then a constant uniform twist in the opposite direction is superimposed. In the plied yarn of the Berry patent the twist is in the singles yarn and the twist in the plied yarn may be in opposite directions. The sections of the plied yarn with Z ply twist can contain singles yarn of S or Z twist and similarly sections of plied yarn with S ply twist can contain singles yarn of both S and Z singles twist.
In a pile fabric, such as a pile carpet, the individual tufts are short. Consequently, a ply yarn carpet tuft of S twist with S singles would not be stable but may tend to unravel. It will not exhibit the same resistance to untwisting as a yarn of correctly balanced opposite twists. Thus, if a carpet were produced using the yarn of the Berry patent, the major portion of the carpet cut pile tufts would consist of unbalanced singles and ply twists and would not be stable. In contrast, in the yarn used in the present invention, all the yarn containing S ply twist contains Z singles and Z ply twist sections contain S twist singles.
It would not be possible to make a cut pile carpet using the process of the Berry patent which would be similar in appearance and wear characteristics to either carpet from normally spun yarn or from the pneumatic self-twist yarn as used in the present invention. A carpet made from yarn of the Berry process would have too high a proportion of the tufts which would vary in appearance, some being thin because the singles yarn twist and the ply twist are in the direction, and others being fat because of opposed single and ply twists.
A major determinant of the appearance of a carpet is the level of singles and ply twists. For example, a high-ply twist results in a frieze carpet, moderate single and ply twist results in a balanced yarn tuft of maximum resistance to untwisting, and very low ply and singles twists give high bulk and low resistance to wear. It would be very difficult using the Berry process to make a carpet of specific characteristics since the twists are all so variable and superimposed event to the extent of twist reversal.
The Shah U.S. Pat. No. 3,775,955 mentions that the composite false twist yarns "may be used to produce pile fabrics, for example, for carpets and upholstery, that are free from streaks, . . . "(col. 1, lines 6-7). The yarn in the U.S. Pat. No. 3,775,955 patent is produced by air jet vortex devices which false twist both single yarns and a plurality of yarns. That patent discusses the problem of untwisting in prior false twisted yarns and states that "application of tension normally results in still further untwisting of such prior art yarns". Twist retention is alleged to occur in the plied yarn of the U.S. Pat. No. 3,775,955 patent because, in one embodiment, there is "a stable balance between ply and single" (col. 3, lines 33-35). However, in Shah's plied yarn there is no attachment of the singles yarns at the nodes and consequently pile fabric formed from such plied yarns may still unwind or unravel when compared to the pile fabric of the present invention.